The overall objective of this research is to isolate and identify metabolites and oxidation products of vitamin A acid (retinoic acid). Metabolites will be isolated from reaction mixtures containing horseradish peroxidase, liver microsomes or heme as catalysts and Fe2 ion or H2O2 as cofactors. Rats and chicks will be fed retinoic acid as their only source of vitamin A and metabolites will be isolated from urine, liver and other tissues. Metabolites will be isolated and purified by high performance liquid chromatography (HPLC) and identified by NMR, IR, UV, and mass spectral analyses.